As for condition relating to value in the rough-I would check out the back glass first for peeling if it's been sitting in area that has had wide temp./humidity fluctuations. It they are just dirty, they might be worth several thousands all together. If moderate to severe damage (playfields, cabinets, glass, mechanicals) would be far less. So condition is everything in a deal like this on your end. I would try to offer a fair price citing condition of games. Sounds like the owner either thinks they are a gold mine (yes, those are mostly very desirable titles), or he doesn't really know a reasonable value?